Common causes of knee and calf soreness are sports strain, joint lesions, degenerative osteoarthropathy, and so on. 1. Exercise strain: Strain on the knee and calf area may cause knee pain and calf soreness. It is commonly caused by long-term weight-bearing walking, sports, etc., which leads to wear and tear of the joint structure and strain of the calf muscles. 2. Knee joint lesions: Structural lesions in the knee joint, such as cartilage wear and tear, meniscus tears, popliteal cysts in the posterior popliteal fossa, cartilage injuries, cruciate ligament injuries can cause knee pain, and the pain can also involve the back of the calf, resulting in lower leg soreness and swelling. 3. Degenerative osteoarthropathy: some elderly people have osteoarthritis due to joint degeneration, which not only manifests as knee pain, but also causes soreness and discomfort in the calf due to contracture of the joint capsule at the back of the joint. If the above symptoms occur, it is recommended to go to the hospital in time for early and regular treatment.